ExpandableListView ruft nicht getChildView auf

private class BadgeListAdapter implements ExpandableListAdapter {

		private ArrayList<ArrayList<Badge>> childList = new ArrayList<ArrayList<Badge>>();
		
		public BadgeListAdapter() throws Exception {
			badgeList = Common.getInstance().api.getBadges(Badges.this);
			
			ArrayList<Badge> myBadges = new ArrayList<FreispielAPI.Badge>();
			ArrayList<Badge> openBadges = new ArrayList<FreispielAPI.Badge>();
			for (Badge badge : badgeList) {
				if(badge.achieved){
					myBadges.add(badge);
				}else{
					openBadges.add(badge);
				}
			}
			
			childList.add(myBadges);
			childList.add(openBadges);
		}
		
		List<FreispielAPI.Badge> badgeList = null;

		@Override
		public boolean areAllItemsEnabled() {
			// TODO Auto-generated method stub
			return true;
		}

		@Override
		public Object getChild(int groupPosition, int childPosition) {
			return childList.get(groupPosition).get(childPosition);
		}

		@Override
		public long getChildId(int groupPosition, int childPosition) {
			// TODO Auto-generated method stub
			return (long)( groupPosition*1024+childPosition );
		}

		@Override
		public View getChildView(int groupPosition, int childPosition,
				boolean isLastChild, View convertView, ViewGroup parent) {

			LayoutInflater inflater = (LayoutInflater) Badges.this
					.getSystemService(LAYOUT_INFLATER_SERVICE);
			View v = inflater.inflate(R.layout.badge_list_child_item, null);
			Badge badge = (Badge)getChild(groupPosition, childPosition);
			((TextView) v.findViewById(R.id.badge_subtitle)).setText(badge.description);
			return v;
		}

		@Override
		public int getChildrenCount(int groupPosition) {
			// TODO Auto-generated method stub
			return childList.get(groupPosition).size();
		}

		@Override
		public Object getGroup(int groupPosition) {
			// TODO Auto-generated method stub
			return null;
		}

		@Override
		public int getGroupCount() {
			// TODO Auto-generated method stub
			return 2;
		}

		@Override
		public long getGroupId(int groupPosition) {
			// TODO Auto-generated method stub
			return (groupPosition*1024);
		}

		@Override
		public View getGroupView(int groupPosition, boolean isExpanded,
				View convertView, ViewGroup parent) {

			LayoutInflater inflater = (LayoutInflater) Badges.this
					.getSystemService(LAYOUT_INFLATER_SERVICE);

			View v = inflater.inflate(R.layout.badge_list_group_item, null);

			if (groupPosition % 2 == 0) {
				v.setBackgroundColor(getResources().getColor(
						R.color.listviewItem_background));
				
				Button header = (Button)v.findViewById(R.id.header_icon);
				header.setText(R.string.my_badges);
			} else {
				v.setBackgroundColor(getResources().getColor(
						R.color.listviewItem_background));
				Button header = (Button)v.findViewById(R.id.header_icon);
				header.setText(R.string.open_badges);
			}

//			((TextView) v.findViewById(R.id.badge_name)).setText(badgeList
//					.get(groupPosition).name);
//
//			((ImageView) v.findViewById(R.id.icon))
//					.setImageDrawable(badgeList.get(groupPosition).icon);

			return v;
		}

		@Override
		public boolean hasStableIds() {
			// TODO Auto-generated method stub
			return true;
		}

		@Override
		public boolean isChildSelectable(int groupPosition, int childPosition) {
			// TODO Auto-generated method stub
			return false;
		}

		@Override
		public boolean isEmpty() {
			// TODO Auto-generated method stub
			return false;
		}

		@Override
		public void onGroupCollapsed(int groupPosition) {
			// TODO Auto-generated method stub

		}

		@Override
		public void onGroupExpanded(int groupPosition) {
			// TODO Auto-generated method stub

		}

		@Override
		public void registerDataSetObserver(DataSetObserver observer) {
			// TODO Auto-generated method stub

		}

		@Override
		public void unregisterDataSetObserver(DataSetObserver observer) {
			// TODO Auto-generated method stub

		}

		@Override
		public long getCombinedChildId(long groupId, long childId) {
			// TODO Auto-generated method stub
			return 0;
		}

		@Override
		public long getCombinedGroupId(long groupId) {
			// TODO Auto-generated method stub
			return 0;
		}

	}